Rice has denied any wrongdoing, saying in an interview with MSNBC the allegations that somehow Obama administration officials "utilised intelligence for political purposes are absolutely false".

The U.S. official said Rice's Trump-related requests were discovered as part of a National Security Council review of the government's policy on "unmasking" - the intelligence community's term for revealing Americans' identities that would otherwise be hidden in classified reports.

Much like his previous allegations that former President Obama had his phones wiretapped, Trump offered no evidence to back up his claims. In many instances, one official said, she did it to understand, per Obama's request, how far Russian meddling in the presidential election had gone and whether or not there was any possible collusion with Trump officials.

Nunes also said he confirmed that "additional names of Trump transition team members were unmasked".

"I have not seen any evidence or any indication of [anything] improper", Warner said.

"I think the committee process can flesh that out and working with the Justice Department, we'll see what actually happens", Collins said in an interview with The Hill.

Trump's post set in motion a sometimes baffling chain of events as the White House and its allies in Congress tried to make the president's charge be true.

"Absolutely false. The intelligence community, the director of the Federal Bureau of Investigation, has made that very clear", she said.

"And the identity of those citizens was revealed, people ought to have the right to know why". The president's advisers quickly embraced Nunes' revelations, but did not acknowledge at the time that the congressman had viewed the information at the White House with the help of White House officials. The president repeatedly refused attempts of the two reporters of New York Times who wished to know what led him to this conclusion, though the President said he would talk more "at the right time". Nunes has said he will not step down from his position as chair of the House Intelligence Committee.